1. Field of the Invention
The invention relates to a lubricator assembly for lubricating a press and, more particularly, to a reciprocating lubricator assembly for lubricating the dies of a die press usable in a forging operation.
2. Discussion of the Related Art
Die presses, sometimes called die forges, are well known for performing die forging metalworking operations. The typical die press includes a bolster having front and rear surfaces and a central opening. Disposed in the central opening are a first, stationary die and a second, movable die in axial alignment with the first die. A casting, sometimes called a forging, is pressed into a desired shape by placing it between the first and second dies and by driving the second die towards the first die under fluid or mechanical pressure to press the casting between the first and second dies and to deform it into the desired shape. The casting is heated in hot forging operations and unheated in cold forging operations. Typical forging operations performed by such presses are open-die forging, closed-die forging, and impression-die forging.
Virtually all forging operations require die lubrication. Applying a lubricant to the dies of a press at the appropriate time reduces friction, thereby 1) reducing die wear and 2) promoting the flow of metal into the die cavities. When used in a hot forging operation, a lubricant also serves as a thermal barrier between the hot casting and the relatively cool dies, thereby slowing the cooling rate of the casting. In addition, the lubricant serves as a parting agent, preventing the casting from sticking to the dies. A wide variety of lubricants can be used in hot forging including graphite, molybdenum disulfate, and sometimes glass. Mineral oils and soaps are commonly used in cold forging.
Lubricant can be applied to the dies either continuously from a stationary lubricator located outside of the press cavity or selectively from a reciprocating lubricator which is positioned outside of the press cavity when the press is closed and which, upon press opening, extends into the press cavity, lubricates the dies, and then retracts from the press cavity before the press closes. Reciprocating lubricators are preferred in many applications 1) because they are positionable to apply lubricant only where it is needed the most, i.e., to the dies, and 2) because they are cleaner than continuously-operating stationary lubricators because they apply lubricant only when it is required.
The most commonly available reciprocating lubricator is a so-called linearly-reciprocating lubricator having a nozzle mounted on the end of an arm which is in turn mounted on a rod of a piston and cylinder device. The arm moves linearly into and out of alignment with the dies upon cylinder extension or retraction. A disadvantage of this type of lubricator is that, because there is a one-to-one correlation between piston stroke and nozzle stroke, and because the linear path of the nozzle requires that it traverse a relatively large distance to move into and out of alignment with the dies, a relatively large cylinder is required. For example, the typical 14" die requires a cylinder stroke of 42" or more to effect the required linear reciprocation of the nozzle.
Marked disadvantageous arise from the requirement of a large cylinder to operate a reciprocating lubricator. For instance, lubricators requiring large cylinders are relatively large, expensive, and cumbersome. Moreover, and perhaps more importantly, the large cylinders required by the typical reciprocating lubricator assembly are relatively slow acting, requiring several seconds for a complete extension/retraction cycle. The lengthy lubrication cycle can significantly increase the length of a forging cycle and reduce a press's production rate.